The processing of product substrates having structures such as chips thereon is often necessary in the semiconductor industry and can comprise mechanical and/or chemical or other processing steps (lithography, resist application, coating, etc.) as well as transport of the product substrates from A to B.
In addition, there is enormous miniaturization pressure at larger and larger radii of the product substrates (200 mm, 300 mm, up to 450 mm) in order to further increase the component density. It can be easily imagined that the handling of these paper-thin product substrates poses major technical problems.
Depending on the carrier materials used and the interconnect layer used between the carrier and the product substrate various methods are known for dissolving or destroying the interconnect layer, such as for example the use of UV light, laser beams, the action of temperature, or solvents.
Stripping increasingly constitutes one of the most critical process steps since the thin substrates, with substrate thicknesses of a few microns, break easily during stripping/removal or are damaged by the forces which are necessary for the stripping process.
Moreover, the thin substrates have little or no stability of shape and typically roll up without support material. During handling of the product substrates which are generally based on back-thinned wafers, fixing and support of the wafers are essentially indispensable.
Known methods for temporary connection of a product substrate to a carrier substrate for easy stripping of the wafer are based for example on double-sided adhesive films, liquids, wax or similar substances so that the product substrate after processing can be separated from the carrier substrate as easily as possible with as little energy as possible. These methods are shown in U.S. Pat. No. 5,725,923, US 2007/0184630, EP 1286385A2 and U.S. Pat. No. 5,863,375.
The following technical problems prevail in temporary connection:
1. High material consumption of partially expensive materials.
2. High temperatures in temporary connection and for this reason high energy consumption.
3. Time-consuming stripping processes, especially in chemical separation/dissolution of the interconnect layer, especially for wet chemical processes which are generally complex, polluting and thus inefficient. In chemical dissolution, incomplete dissolution of the interconnect layer prior to stripping of the product substrate can result in some sites continuing to act adhesively, which can lead to destruction of the product wafer during stripping at these sites.
4. Cleaning of the product substrate after stripping is necessary.
It is therefore the object of this invention to devise a method for temporarily connecting a product substrate on a carrier substrate as nondestructively as possible and with the minimum possible energy expenditure, wherein the product substrate can again be easily detached from the carrier substrate.
This object is achieved with the features of the claims. Advantageous developments of the invention are given in the dependent claims. All combinations of at least two of the features given in the specification, the claims and/or the figures also fall within the scope of the invention. At the given value ranges, values within the indicated limits will also be considered to be disclosed as boundary values and will be claimed in any combination.